After a painful, ultimately unsuccessful in-place upgrade to 2.4.4 from 2.4.3-p1, I needed to rebuild my config by hand (the box was unstable, igb0 (WAN) was physically linking and unlinking every 2 seconds). I think I found at least one of the issues. If you have an interface using IPv6 by tracking another interface, the Prefix ID cannot be altered to get different subnets. There seems to be a validation bug in the field code. It says the valid hex values are "0 to 0". This is not just a label issue as you cannot save the prefix value either. This was working find in 2.4.3-p1.